In general, a maxillary skeletal expander, a device used for a treatment of a patient whose upper jaw is less developed than the lower jaw, serves to expand the upper jaw to facilitate a treatment. Facial bones act like puzzle making, so bones may be easily moved during a growth period, and an upper jaw is composed of several bones engaging with one another, rather than being a single bone. If an upper jaw is too small to accommodate permanent tooth, a bone portion in the center of a ceiling of a mouth may be outstretched to expand a maxillary arch itself.
FIG. 1 is a view illustrating a conventional art maxillary skeletal expander. The related art maxillary skeletal expander is fixed to a maxillary arch A and includes a pair of bodies 1, arms 2 fixed to the bodies 1, an extending screw 3 adjusting a space between the pair of bodies 1, a guide rail 4 guiding a movement of the bodies 1 when a space between the bodies 1 is adjusted, key a hole 5 formed in the extending screw 3 allowing the extending screw 3 to rotate when a rotational key is inserted thereinto and rotated, and a fixing part 6 combined with the arms 2 so as to be fixed to the teeth B of a patient. When a key is inserted into the key hole 5 to rotate the extending screw 3, the bodies 1 are moved in a direction toward the teeth B on both sides and a space between the bodies 1 is opened, whereby the maxillary skeletal expander expands the fixed upper jaw. However, in the case of the related art maxillary skeletal expander, since the fixing part 5 is fixed to the teeth B, rather than to the maxillary arch A, the maxillary arch A is not expanded and only the teeth B are gapped in many cases.
In order to solve the problem, a maxillary skeletal expander using mini-screws has been developed. In this case, the maxillary skeletal expander is fixed to the maxillary arch A with screws. FIG. 2 is a view illustrating a related art maxillary skeletal expander using mini-screws. The maxillary skeletal expander using mini-screws includes a pair of bodies 10, arms 20 fixed to the bodies 10, an extending screw 30 adjusting a space between the pair of bodies 10, a guide rail 40 guiding a movement of the bodies 10 when a space between the bodies 10 is adjusted, a key hole 50 formed in the extending screw 30 allowing the extending screw 30 to rotate when a rotational key is inserted thereinto and rotated, and a fixing part 60 combined with the arms 20 so as to be fixed to the teeth B of a patient. Also, the related art maxillary skeletal expander further includes hooks 70 allowing mini screws to be implanted therein to fix the bodies 10 to an upper jaw. The hooks 70 serve to fix the bodies 10 to an upper jaw when mini-screws are implanted therein, but the hooks 70 are disadvantageous in that they cannot guide the mini screws to be perpendicular to a direction in which the bodies 10 are expanded, resulting in that the mini-screws are implanted slantingly. Also, when the mini-screws are implanted in the hooks 70, the mini-screws are not vertically implanted during an implanting process, failing to properly transmit force when expanding, and the mini-screws may be loosened or the hooks 70 are bent.